The long-term goal of this project is to elucidate the role of peptidergic nerve fibers in modulating taste cell function. Using various configurations of the patch-clamp recording technique on isolated taste cells from the mudpuppy and hamster, I will test the following hypothesis: A function of neuropeptides in the vertebrate taste bud is to modulate transduction, either directly by altering the membrane properties of the taste receptor cell, or indirectly by altering the efficacy of synaptic transmission between taste cells and intragemmal nerve fibers. Specifically, I will test this hypothesis by answering the following questions: 1. What neuropeptides are present in mudpuppy and hamster lingual epithelium? 2. What are the effects of specific neuropeptides on membrane properties of mudpuppy taste cells? Do neuropeptides modulate voltage-dependent conductances in taste cells and do neuropeptides influence the transduction of taste stimuli into receptor potentials? 3. What are the basic membrane properties of hamster taste cells? Do hamster taste cells have voltage-dependent conductances similar to those of the mudpuppy? What are the mechanisms involved in the transduction of sweet taste stimuli into receptor potentials? 4. What are the effects of specific neuropeptides on membrane properties of hamster taste cells? Do neuropeptides influence taste transduction on hamster taste cells? 5. Do compounds which stimulate collaterals of peptide- containing nerve fibers, such as capsaicin, effect the afferent nerve response to particular taste stimuli in the mudpuppy and hamster? These studies will provide important information concerning the effect of capsaicin exposure on the physiology of taste, and the relationship between the common chemical sense and the sense of taste. In addition, since neuropeptides are found throughout the nervous system, results from these studies may well provide a general model for mechanisms involved in peptidergic modulation of neuronal membranes.